this is very a impressive combo. the log below shows a game where i pull the trigger on turn 12 for 8 provinces. Playing with shelters helps this combo. Necropolis helps you play two Hermits for two Market square and two madmen.
For a piledrive on provinces you need 19 Golds + 7 coppers for exactly 64 coins. if you pull the trigger with 5 Market Squares, you can gain MS 6+7+8 while you go off. this gives you 5+6+7=18 golds, so you need to get at least 1 gold before that turn.
In my example i had to trash a Market Square during the megaturn, because i had only 2 extra cards in my deck, so i got only 17 golds, but i had got 2 golds on hermit trashes beforehand. So take good care of your starting estates/shelters.
http://dominionlogs.goko.com//20130207/log.50955175e4b013548a3d58f0.1360271535775.txtStopping this combo seems rather difficult. In the sample game there was Minion, who does usually a good job in disrupting combos, but Minion does not slow down the combo. So the only defense might actually be to deny combo pieces.